Field of the Invention
The invention relates to a switch unit, an Ethernet network comprising a switch unit and a method for activating components in an Ethernet network.
Description of the Background Art
Ethernet networks have long been known from the field of computer science, and their use in motor vehicles has been contemplated in recent years. One advantage of Ethernet networks over conventional automotive networks, such as CAN or FlexRay, is that they very easily permit subnetwork operation, so that unnecessary control units may be switched off or placed in sleep mode. This makes it possible to correspondingly save electrical energy.
A method for activating at least one temporarily inactive network component of a network system for a motor vehicle is known from DE 10 2010 008 818 A1, which corresponds to U.S. Pat. No. 9,413,549, a central network device of the network system being connected to the network component via signals by a path within the network system. The path at least partially leads over a network segment of the network system, the network segment connecting, via signals, the network component and a first activation device assigned thereto to a switch device arranged in the path and to a second activation device assigned thereto in an unbranched manner. The central network device addresses the first activation device with the aid of the switch device by sending a network function control signal. The network system is preferably an Ethernet network. The disadvantage of central approaches of this type is that the failure of this central component results in the total failure of the network.
A method for activating deactivated control units of a vehicle in a vehicle network is known from DE 10 2012 207 858 A1, which corresponds to US 2015/0131477, in which the control units of the vehicle, which form the nodes of the vehicle network, are able to communicate with each other, a group of control units of the vehicle, which are to be activated and are in communication with each other, being combined into a subnetwork to be activated. Each node has at least one network interface to an adjacent node, which is directly addressable via this network interface, and also has a subnetwork management system. The subnetwork management system specifies the network interface via which the node of the vehicle network may communicate with which subnetwork; in the presence of an activation command for the control units of a subnetwork in the subnetwork management system, a node identifies which of its network interfaces it is able use to communicate with the subnetwork to be activated, the node subsequently transmitting the activation command to the adjacent nodes via the identified network interfaces. The adjacent node is then activated by transmitting the activation command if the node was deactivated prior to the transmission of the activation command. This type of communication setup may also be referred to as step-by-step wakeup. However, this method has the disadvantage that it is slow, depending on the number of control units or switch devices to be woken up. Interactive electrical systems usually are to respond without noticeable delay in the vehicle. However, it may take as long as 200 ms to set up a connection between two directly connected control units.
One possible solution to this time problem is a global wakeup. For this purpose, the switch units (or switch devices) may have hardware which ensures that, as soon as activity is detected on one link (before the communication is established), all other links are also woken up directly. As a result, all links in the vehicle start up almost simultaneously as soon as a control unit has a need for communication (i.e., after approximately 200 ms). As soon as all control units are awake and determine that they are, in fact, not needed, they may be shut down and turn themselves off, coordinated via the communication established up to that point. The shutdown may occur, for example, via a network management protocol. This is not an optimum approach from an energy perspective.